"He was a true genius."

In a Facebook post Saturday, Clapton also tells how the artist inspired him to write the song "Holy Mother."

Clapton recalled a period in the 1980s when he was on the road and caught in what he called a "downward spiral with drink and drugs."

Then he saw Prince's Purple Rain in a Canadian movie theater and, Clapton said, it hit him like a bolt of lightning. The musician said he went back to his hotel and, amid empty beer cans, and wrote "Holy Mother."

Clapton wrote on Facebook that he can't believe Prince is gone.

The 57-year-old was found dead Thursday in his suburban Minneapolis home, with the cause of death unknown.